Co2 utilization in molten salt reactor (msr) for ultra energy efficiency and reduced emissions

ABSTRACT

A system for a carbon neutral cycle of gas production may include a molten salt reactor configured to generate zero carbon dioxide (CO 2 ) emissions electricity. The system may include a desalination unit configured to receive the zero-CO 2  emissions electricity from the molten salt reactor and produce a desalinated water. The system may include an electrolysis unit configured to be powered by the zero-CO2 emissions electricity generated by the molten salt reactor and generate hydrogen (H 2 ) and oxygen (O 2 ) from the desalinated water. The system may include an oxy-combustion unit configured to receive and combust a hydrocarbon fuel with the O 2  from the electrolysis unit to produce electricity and CO 2 . The system may include a CO 2  capture system adapted to capture the CO 2  produced by the oxy-combustion unit and a catalytic hydrogenation unit configured to receive and convert H 2  from the electrolysis unit and CO 2  from the CO 2  capture system to produce the hydrocarbon fuel.

BACKGROUND

As global demand for energy grows, greenhouse gas emissions into theearth's atmosphere also increase. This growth in greenhouse gasemissions disrupts the balance of the Earth's ecosystem and affects alllife. Greenhouse gases, particularly carbon dioxide (CO₂), undesirablyabsorb and emit radiation within the atmosphere, causing a “greenhouseeffect.” Attention to curb greenhouse gases has focused on CO₂ emissionsdue to the ever-increasing combustion processes emitting CO₂ as a wasteproduct into the environment.

Lawmakers, worldwide, have also focused their efforts in cutting CO₂emissions by pushing carbon neutrality, legislating the development ofnew technologies and changing tax, penalty, and incentive programs tocut down on CO₂ emissions and develop new carbon neutral integrativeprocesses.

The increase in CO₂ emissions has led to the development of CarbonCapture, Utilization and Storage (CCUS). CCUS is a set of technologiesthat is used to capture carbon dioxide emissions at the source, thuspreventing the CO₂ from entering the atmosphere. The CO₂ emissions aretransported away and may be either stored deep underground or turnedinto useful products. Capturing CO₂ has been used to help improve thequality of natural gas. As the field continues to innovate, CO₂ may beremoved and sequestered indefinitely. Moreover, it may also be turnedinto a marketable industrial commercial product, thus adding value to anotherwise harmful waste stream.

Accordingly, there exists a need for innovations in carbon (dioxide)capture and storage capabilities.

SUMMARY

This summary is provided to introduce a selection of concepts that arefurther described below in the detailed description. This summary is notintended to identify key or essential features of the claimed subjectmatter, nor is it intended to be used as an aid in limiting the scope ofthe claimed subject matter.

In one aspect, embodiments disclosed herein relate to a system for acarbon neutral cycle of gas production. The system may include a moltensalt reactor configured to generate zero carbon dioxide (CO₂) emissionselectricity. A desalination unit may be provided and configured toreceive the zero-CO₂ emissions electricity from the molten salt reactorand produce a desalinated water. An electrolysis unit may also beprovided and configured to be powered by the zero-CO₂ emissionselectricity generated by the molten salt reactor and generate hydrogen(H₂) and oxygen (O₂) from the desalinated water. The system may alsoinclude an oxy-combustion unit configured to receive and combust ahydrocarbon fuel with the O₂ from the electrolysis unit to produceelectricity and CO₂. The system may also provide a CO₂ capture systemadapted to capture the CO₂ produced by the oxy-combustion unit and acatalytic hydrogenation unit configured to receive and convert H₂ fromthe electrolysis unit and CO₂ from the CO₂ capture system to produce thehydrocarbon fuel.

In another aspect, embodiments disclosed herein relate to a method for acarbon neutral cycle of a natural gas production. The method may includegenerating electricity with a molten salt reactor configured to generatezero carbon dioxide (CO₂) emissions. The method may also includepowering a desalination unit with the electricity from the molten saltreactor, producing desalinated water (H₂O) with the desalination unit.The method may include producing hydrogen (H₂) and oxygen (O₂) from thedesalinated water (H₂O) with an electrolysis unit and introducing the H₂produced by the electrolysis unit to a catalytic hydrogenation unit. Themethod may include reacting captured CO₂ and the H₂ generated from thedesalination unit by catalytic hydrogenation in a catalytichydrogenation unit, wherein the reaction produces a hydrocarbon fuel.The method may also include introducing the hydrocarbon fuel into anoxy-combustion unit and producing CO₂ in the oxy-combustion unit byreacting the hydrocarbon fuel with the O₂ from the electrolysis unit.The method may also include capturing CO₂ from the oxy-combustion unitand introducing the captured CO₂ to the catalytic hydrogenation unit.

Other aspects and advantages of the claimed subject matter will beapparent from the following description and the appended claims.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a flow diagram of a CO₂ utilization and value creation processaccording to embodiments of the present disclosure.

FIG. 2 is a schematic of an exemplary molten salt reactor system.

DETAILED DESCRIPTION

Embodiments of the present disclosure relate to the fields of CO₂utilization and value creation. Embodiments of the present disclosurerelate to systems and methods of using green (clean) electrical energywith zero CO₂ emissions generated by a molten salt reactor (MSR) toconvert CO₂ into commercial products for a carbon neutral life cycle.

The capture and conversion of CO₂ is useful across industrial andcommercial applications, such as the production of methane (CH₄) andmethanol (CH₃OH). Carbon capture and storage is a central part ofefforts to achieve net zero CO₂ and other greenhouse gas emissions,while also ensuring the world can continue to innovate and thrive.Capturing carbon has been used to help improve the quality of naturalgas, but has fallen short of turning CO₂ into a marketable industrialand commercial product while also achieving carbon neutrality.

Embodiments of the present disclosure relate to CO₂ utilization andvalue creation. CO₂ may be captured and converted into useful industrialproducts. The driving energy of the CO₂ conversion is clean electricitygenerated with zero CO₂ emission operation, such as molten salt reactoroperations.

FIG. 1 shows an embodiment of the overall CO₂ utilization and valuecreation process 100 of the current disclosure. In the embodiment shownin FIG. 1, CO₂ may be captured from a natural gas production process101, such as a natural gas production plant gas sweetening process, andenter line 112. It will be understood by those skilled in the art thatCO₂ may be captured from other sources, including cement factories,biomass power plants, oil refineries, and other heavy industrialsources, particularly those that burn fossil fuels.

The captured CO₂ may be fed into a catalytic hydrogenation unit 103through line 102. In the catalytic hydrogenation unit 103, hydrogen (H₂)may enter in through line 104, wherein it may react with the CO₂ fromline 102 to produce a hydrocarbon fuel, such as CH₄. The H₂ may beproduced from an electrolysis unit 105 connected to the catalytichydrogenation unit 103 via line 104. The CH₄ may flow through line 106and into the natural gas grid 107. Although the embodiment shown in FIG.1 shows the production of CH₄, it will be understood by those skilled inthe art with the benefit of the current disclosure that otherhydrocarbon fuels, such as CH₃OH, may be produced in embodiments of thepresent disclosure.

As shown in FIG. 1, some embodiments may have an oxy-combustion unit 108fluidly connected to the catalytic hydrogenation unit 103 and thenatural gas grid 107 via line 106 and line 109. CH₄ may be injected intothe oxy-combustion unit through line 109 wherein it may react withoxygen (O₂) from line 110 to produce a CO₂ stream in line 111. The O₂may be produced in the electrolysis unit 105 connected to theoxy-combustion unit 108 via line 110. The CO₂ produced by theoxy-combustion unit 108 and flowing through line 111 may be captured andcombined with the CO₂ from the natural gas production process 101flowing though line 112. The combined captured CO₂ may be stored in aCO₂ storage unit 113 until the CO₂ is fed into the catalytichydrogenation unit 103 via line 102.

It will be understood by those skilled in the art that the captured CO₂from the natural gas production process 101 and the CO₂ from theoxy-combustion unit 108 may not be stored in the same storage unit. Itwill also be understood by those in the art that the captured CO₂ fromthe natural gas production process 101 and the captured CO₂ from theoxy-combustion unit 108 may be directly connected to the catalytichydrogenation unit 103, either separately/independently of each other orthrough a combined line wherein both captured CO₂ streams (line 111 andline 112) fluidly connect in a single line 102 to the catalytichydrogenation unit 103 (not shown in the FIG. 1 embodiment).

In embodiments of the present disclosure, the combined captured CO₂ (asshown stored in CO₂ storage unit 113), the CO₂ in line 102, thecatalytic hydrogenation unit 103, the CH₄ in line 106, the natural gasgrid 107, the CH₄ flowing in line 109, the oxy-combustion unit 108, andthe CO₂ in line 111, or any combination thereof, may form a carbonneutral natural gas cycle.

In embodiments of the present disclosure, the driving energy of theoverall CO₂ utilization and value creation process 100 may beelectricity generated by a molten salt reactor 114. As shown in FIG. 1,a molten salt reactor 114 may generate electricity. The molten saltreactor 114 may generate clean/green electricity, wherein the moltensalt reactor 114 does not release CO₂ into the atmosphere.Oxy-combustion unit 108 may also be used to produce electricity, usedwithin the carbon-neutral natural gas cycle (113→103→107→108→113) and/orexported; energy from the oxy-combustion unit 108 may also oradditionally be used for other processes requiring radiant or convectiveheat or transformation into work, such as via a turbine.

In embodiments of the present disclosure, the electricity generated fromthe molten salt reactor 114 may be used to desalinate seawater. Theelectricity may flow from the molten salt reactor 114 through line 115to provide power to the desalination of seawater in desalination unit116. The high salinity water, brine, and/or salts produced from thedesalination unit 116 may be used in an enhanced oil recovery unit 117.The desalination unit 116 may be incorporated into the enhanced oilrecovery unit 117, wherein the high salinity water, brine, and/or saltsmay be injected into oil-bearing reservoirs to maintain the reservoirpressure and improve secondary hydrocarbon recovery. The water (H₂O)product stream from the desalination unit 116 may flow through line 118to an electrolysis process.

As shown in FIG. 1, the H₂O from the desalination unit 116 may flowthrough line 118 to an electrolysis unit 105. In the electrolysis unit105, the H₂O may be decomposed into O₂ and H₂ in an electrolysisreaction. The electrolysis reaction may also be powered by theelectricity generated in the molten salt reactor 114. The electrolysisof H₂O in the electrolysis unit 105 may produce an O₂ stream in line 110and a H₂ stream in line 104. The O₂ stream in line 110 may be connectedto the oxy-combustion unit 108 via line 110 wherein it may provide O₂for the oxy-combustion reaction. The H₂ stream may be connected to thecatalytic hydrogenation unit 103 via line 104 wherein it may provide H₂for the catalytic reaction with CO₂ to form a methane product. The H₂produced in the electrolysis of H₂O may also be connected via line 119to be used in other industrial applications 120, such as refineryapplications, fuel cells, and hydrogenation.

In one aspect, embodiments disclosed herein relate to CO₂ captured fromindustrial operations. An example of a source for captured CO₂ is aconventional natural gas plant. Natural gas with carbon capture usespost-combustion capture methods. CO₂ is a product of burning naturalgas. Post-combustion capture of CO₂ is a conventionally availableintegrated operation of natural gas combined cycle plants. Methods ofCO₂ separation/removal from a natural gas emission may includemembrane-based systems and filter systems. The high cost of efficiencypenalties associated with carbon capture and storage, as well as methaneleakage from natural gas extraction and distribution limit the benefitof carbon capture and storage on reducing greenhouse gases. Someembodiments of the present disclosure may use the captured CO₂ of anatural gas production plant in a subsequent, downstream, value-addedprocess to ensure the CO₂ is not released into the atmosphere.

In some embodiments of the present disclosure, conventional natural gasplants capture CO₂ in a gas sweetening process. Gas sweetening is theprocess of removing hydrogen sulfides, carbon dioxide, and mercaptansfrom natural gas to make it suitable for transport and sale. It isdesirable to sweeten natural gas because H₂S and CO₂ have a corrosiveeffect on gas pipelines. The CO₂ is removed, captured from the pipelineand either stored in facilities or used in processes that use CO₂, andnot released into the atmosphere as greenhouse gases.

In embodiments of the present disclosure, captured CO₂ may be used in acatalytic hydrogenation process. Catalytic hydrogenation of the presentdisclosure produces methane or methanol from CO₂ (from a captured CO₂stream) and H₂ (e.g., from an electrolysis process). Catalytichydrogenation may be used to convert CO₂ and H₂ into a usablehydrocarbon-based fuel, including methane (CH₄) and methanol (CH₃OH).The conversion of CO₂ into methane or methanol is the prime targetreactions in catalytic hydrogenations of the present disclosure, asshown below:

CO₂+4H₂

CH₄+2H₂O ΔH_(298 K)=−165.0 kJ mol⁻¹

CO₂+3H₂

CH₃OH+H₂O ΔH_(298 k)=−49.4 kj mol⁻¹

To catalyze the reaction between CO₂ and H₂, surface sites that bind andactivate CO₂ need to co-exist and cooperate with sites for dissociationof H₂. Activation of CO₂ by heterogeneous catalysis is often carried outusing conventional reducible oxides, including ceria, zirconia, ortitania, while metals are conventionally used to dissociate H₂. It isdesirable to use a catalyst that can efficiently and effectivelysuppress the formation of by-products in favor of the formation ofmethane or methanol.

Hydrogenation of CO₂ to methane is thermodynamically favorable overother CO₂ conversion reactions. Different transition metals, such as Ru,Rh, Ni, and Pd have been known to be highly selective and active for themethane formation by CO₂ hydrogenation, particularly at lowtemperatures. The supported Ni catalysts conventionally have the highestselectivity to form methane.

Catalytic hydrogenation of CO₂ with H₂ to produce CH₄ and CH₃OH has awide range of applications, including the production of syngas and theformation of compressed natural gas. It is a key pathway for CO₂recycling and it can offer a solution for renewable H₂ storage andtransportation. In parallel, the CO₂ hydrogenation reactions to produceCH₄ and/or CH₃OH are considered to be useful in reclaiming oxygen (O₂)within a closed cycle. Catalytic hydrogenation of CO₂ to produce CH₄and/or CH₃OH requires substantial amounts of H₂.

In embodiments of the present disclosure, the CO₂ capture and catalytichydrogenation unit may be oversized, thus producing a surplus of CH₄and/or CH₃OH. This oversized unit may improve the unit operations andefficiency of scale. A portion of the CH₄ or CH₃OH product stream froman oversized unit may be fed to a downstream process. For example, inembodiments of the present disclosure, CO₂ may be catalyticallyhydrogenated into CH₃OH, wherein the CH₃OH is injected into the naturalgas grid. The CH₃OH produced by catalytic hydrogenation may also beinjected/fed into an oxy-combustion process to produce electricity.CH₃OH, as produced by embodiments of the present invention, may be usedas a feedstock for chemicals, such as ethylene or propylene through amethanol to olefin process.

H₂ may be produced by a number of processes, but industrially ispreferentially produced using non-renewable feedstocks. Hydrogenproduction is also generally considered an expensive undertaking,particularly with methods such as steam methane reforming.

Steam methane reforming is one of the most commonly used commercializedmethods of producing hydrogen. Steam methane reforming produces hydrogen(syngas) by reaction of hydrocarbons with water. The reaction is oftenconducted under high pressure mixture of steam and methane in thepresence of a nickel catalyst. In some steam methane reformingprocesses, a desulfurized hydrocarbon feedstock (e.g., natural gas) ispreheated, mixed with steam and passed over a catalyst to produce carbonmonoxide, carbon dioxide, and hydrogen, wherein the hydrogen issubsequently separated. Steam methane reforming accounts for themajority of the worlds produced hydrogen, but is not considered aclean/green resource due to its production of greenhouse gases. Thus, itis desirable to decrease CO₂ emissions wherein the H₂ necessary for thecatalytic hydrogenation is sourced from a clean, renewable resource. Anexample of a clean resource that produces hydrogen is water electrolysispowered by green energy.

Water electrolysis is considered an effective alternative to steammethane reforming for the production of H₂. In embodiments of thepresent disclosure, electrolysis of H₂O produces the H₂ used in thecatalytic hydrogenation process. The hydrogen production process in thepresent disclosure may be connected to an energy source, such as amolten salt reactor, to power the electrolysis reaction.

A molten salt reactor (MSR) is a nuclear fission reactor that usesmolten fluoride salts as a primary coolant at low pressure, whereinfissile and fertile fuel may be dissolved in the salt instead of fuelrods. FIG. 2 shows a schematic of an exemplary MSR system 200. As shownin FIG. 2, fuel is dissolved within a fluoride salt mixture, producingeither uranium fluoride or thorium fluoride inside a reactor tank 210and circulated around a reactor core unit 202 via circulation motors201. The reactor core unit 202 may include a graphite reactor coredefining an internal space that houses one or more fuel wedges 216. Thefuel salt flows through line 203 to a heat exchanger 204 where it isused to heat solar salt that enters the primary heat exchanger 204through line 205. The heated solar salt exits the primary heat exchanger204 through line 206 wherein it enters a steam generator 207. The heatfrom the solar salt is used to heat water entering the steam generator207 through line 208. The water is heated under high pressure in thesteam generator 207 and exits through line 209 as steam. The cooledsolar salt is pumped via salt circulating pump 211 back to heatexchanger 204. The steam from line 209 drives turbine 212 by operationsunderstood by those skilled in the art. The turbine rotates a shaft 215connected to a generator 213. The generator 213, in turn, converts themechanical energy to electrical energy based on mechanisms understood bythose skilled in the art.

The arrangement and operation of MSRs vary according to designspecifications. For example, the use of molten salt as fuel and ascoolant are independent design choices. The originalcirculating-fuel-salt MSR and the more recent static-fuel-salt stablesalt reactor use salt as fuel and salt as coolant; a dual fluid reactoruses salt as fuel but metal as coolant; and the fluoride salt-cooledhigh temperature reactor has solid fuel but salt as coolant.

Although MSRs operate on the same basic principle as other nuclear powerreactors (controlled fission to produce steam that powerselectricity-generating turbines), MSRs offer advantages overconventional nuclear power plants. As in all low-pressure reactordesigns, MSRs achieve passive decay heat removal. In some designs, thefuel and the coolant may be the same fluid, so a loss of coolant removesthe reactor's fuel, similar to how loss of coolant also removes themoderator in light water reactions. Unlike steam in alternativereactors, the fluoride salts of MSRs dissolve poorly in water and do notform burnable hydrogen. Also, molten salts are not damaged by the core'sneutron bombardment, unlike steel and solid uranium oxide in otherreactors.

Some reactors, such as a boiling water reactor (BWR), utilize highpressure radioactive steam that may leak the radioactive steam andcooling water, requiring expensive containment systems, piping, andsafety equipment. MSRs advantageously utilize low pressure with a lowerrisk of leakage. However, most MSR designs require fluid withradioactive fission product in direct contact with pumps and heatexchangers.

Other advantages of MSRs include cheaper closed nuclear fuel cyclesbecause they can operate with slow neutrons. If fully implemented,reactors that close the nuclear fuel cycle may reduce environmentalimpacts. For example, chemical separation may turn long-lived actinidesback into reactor fuel. The MSR fuel's liquid phase might bepyroprocessed to separate fission products (nuclear ashes) from actinidefuels. The discharged wastes generally have shorter half-lives. Thisreduces the need for geologic containment to 300 years rather than thetens of thousands of years as needed by a light-water reactor's spentnuclear fuel. It also permits the use of alternate nuclear fuels, suchas thorium.

It is also notable that fuel rod fabrication is not required in MSRs, asthey are replaced with fuel salt synthesis. Some MSR designs arecompatible with the fast neutron spectrum, which can pyroprocessproblematic transuranic elements like Pu240, Pu241 and up (reactor gradeplutonium) from traditional light-water nuclear reactors.

An MSR can react to load changes in less than 60 seconds (unlike“traditional” solid-fuel nuclear power plants that suffer from xenonpoisoning). Molten salt reactors can run at high temperatures, yieldinghigh thermal efficiency. This reduces size, expense, and environmentalimpacts. MSRs can offer a high “specific power,” that is high power at alow mass. A possibly good neutron economy makes the MSR attractive forthe neutron poor thorium fuel cycle.

A notable advantage of the MSR as a source of energy in embodiments ofthe present disclosure is that the energy produced by MSR may beconsidered a green energy, in that it may not produce CO₂ emissions.This green energy may be utilized in embodiments of the presentdisclosure to power desalination of seawater to create H₂O, wherein theH₂O is ultimately used to produce the H₂ for the catalytic hydrogenationprocess described above.

Embodiments of the present disclosure may include a desalinationprocess, wherein H₂O may be produced by desalination of seawater (waterwith dissolved salt and other minerals). Desalination refers to theremoval of salts and other minerals from a target substance, likeseawater. In desalination, salt water (seawater) is fed into acontainer. Feed sources may include brackish, seawater, wells, rivers,streams, wastewater, and industrial feed and process waters.

Desalination processes may use membrane separation techniques. Saltwater may pass through a semipermeable membrane. The membrane filtersthe salt and minerals from the salt water, producing H₂O (fresh water).Membrane separation requires a high driving force, including appliedpressure, vapor pressure, electric potential, and concentration toovercome natural osmotic pressures and effectively force water through atarget membrane. As such, desalination is an energy intensive process.It is conventionally powered by fossil fuel processes, therebycontributing the CO₂ emissions. Reverse osmosis (RO) and nanofiltration(NF) are the leading pressure driven membrane processes. Membraneconfigurations include spiral wound, hollow fiber, and sheet with spiralbeing the most widely used. Contemporary membranes are primarilypolymeric materials with cellulose acetate still used to a much lesserdegree. Electrodialysis (ED), electrodialysis reversal (EDR), forwardosmosis (RO), and membrane distillation (MD) are also membrane processesused in desalination.

Embodiments of the present disclosure may power the desalination processwith the energy generated by a molten salt reactor. As described above,the energy from the MSR in embodiments of the present disclosure may begenerated without producing CO₂ emissions. By using the energy createdby a MSR with zero/negligible CO₂ emissions as the driving force for thedesalination of seawater instead of conventional methods that burnfossil fuels, less CO₂ is released into the atmosphere.

Embodiments of the present disclosure may use the concentrated saltwater, brine, and/or salts produced by the desalination in an enhancedoil recovery (EOR) process. The desalination partially or fully removesH₂O from seawater, producing pure water (H₂O) and either high salinitywater, brine, or salts, depending on the extent of the H₂O removal. EORmay use the high salinity water (or add the salts to water to createhigh salinity water) in water flooding techniques. Water flooding may beused as a secondary method to improve oil recovery. Oil pressuresdecline during oil production, leading to a reduction in oilproductivity. EOR methods, such as water flooding, inject high-salinitywater into target reservoir zones to maintain, support, or increase thereservoir pressure and oil productivity. The high salinity water andsalts produced by the desalination of embodiments of the presentdisclosure may be used in these EOR.

Embodiments of the present disclosure may use the high salinity, brine,or salts for other industrial applications, such as cooling water forpower generation, aquaculture, and for a variety of other uses in theoil and gas industry, such as drilling and hydraulic fracturing.

Embodiments of the present disclosure may use the H₂O produced in thedesalination process to produce H₂ and O₂ streams via electrolysis. TheH₂ produced may be used in the catalytic hydrogenation process and theO₂ may be used in an oxy-combustion process. Electrolysis (i.e.,water-splitting) of H₂O produces H₂ and O₂ from renewable resources byusing electricity to split water molecules. Electrolysis may occur in avessel called an electrolyzer. The electrolyzer may be configured tohouse an anode and a cathode. The anode and cathode may be connected topower source. H₂ will form at the cathode and O₂ will form on the anode.

In some embodiments, the anode and cathode may be separated by anelectrolyte. The efficiency of the electrolysis process may be increasedthrough the addition of an electrolyte, as well as the use of anelectrocatalyst. Electrolyzers may function in different ways dependingon the type of electrolyte material used in the process. Examples ofdifferent electrolyzers include polymer electrolyte membraneelectrolyzers, alkaline electrolyzers, and solid oxide electrolyzers.The electrolysis process may be scaled depending on production facilityrequirements.

H₂ produced via electrolysis may result in zero greenhouse gasemissions, depending on the source of the electricity used. The sourceof the required electricity, the electricity cost and efficiency, aswell as emissions resulting from electricity generation must beconsidered when evaluating the benefits and economic viability ofhydrogen production via electrolysis. In embodiments of the presentinvention, the electricity from the MSR may drive the electrolysisprocess, resulting in zero/negligible CO₂ emissions when producing thehydrogen and oxygen.

In embodiments of the present disclosure, the hydrogen produced viaelectrolysis may be used in the catalytic hydrogenation process with CO₂to produce CH₄ and CH₃OH. CH₄ and CH₃OH are considered valuableindustrial products and fuels. Other applications for the H₂ produced inthe electrolysis reaction may include refinery hydrogenation operationsand other hydrogen economy applications, such as fuel cell powereddevices (e.g., cars).

O₂ is also a product of electrolysis. In embodiments of the presentdisclosure, the O₂ produced by the electrolysis process is fed into anoxy-combustion process. In the oxy-combustion process, a fossil fuel,such as CH₄, is burned in the presence of O₂ instead of air to produceCO₂, H₂O (water vapor), and electricity. O₂ increases combustionefficiency and the concentration of CO₂ in flue gasses, therebyimproving CO₂ capture. The H₂O may be condensed through cooling and theCO₂ stream may be captured. The increased CO₂ concentration in flue gasmay enable the capture of CO₂ with a reduced NOx (nitrogen oxides)emission due to the purity of the O₂ feed from the O₂ produced by theelectrolysis process. In the oxy-combustion process of embodiments ofthe present disclosure, CH₄ is fed to the oxy-combustion process andreacted with O₂ to create CO₂. The oxy-combustion reaction inembodiments of the present disclosure is shown below:

CH₄+2O₂→CO₂+2H₂O

The source of CH₄ may include the CH₄ produced in the catalytichydrogenation unit, CH₄ from a natural gas grid, and a combination ofboth the CH₄ produced in the catalytic hydrogenation unit and naturalgas grid.

In embodiments of the present disclosure, CH₃OH, and not CH₄, may beproduced in the catalytic hydrogenation unit and fed into theoxy-combustion unit to produce electricity. In the embodiments thatproduce CH₃OH, the O₂ from the electrolysis unit reacts with the CH₃OHin the oxy-combustion unit to produce CO₂, H₂O (water vapor), andelectricity. The oxy-combustion reaction of the methanol reaction withO₂ is shown below:

2CH₃OH+3O₂→2CO₂+4H₂O

In embodiments of the present disclosure, the CO₂ from theoxy-combustion reaction may be captured. The captured CO₂ from theoxy-combustion reaction may be stored with the CO₂ captured from thenatural gas plant. The combined captured CO₂ streams may thereby be fedto the catalytic hydrogenation process, wherein it is reacted with theH₂ to create CH₄ or CH₃OH. It will be appreciated by those skilled inthe art and the benefit of the present disclosure that the production ofCH₄ or CH₃OH using embodiments of the present disclosure may be a designchoice and depend on the industrial application utilizing embodiments ofthe present disclosure.

Embodiments of the overall CO₂ utilization and value creation process ofthe current disclosure may capture and process CO₂ using clean energy toreduce CO₂ emissions in industrial operations. In embodiments of thecurrent disclosure, CO₂ captured from industrial processes, such asnatural gas sweetening processes, may be combined with CO₂ produced byan oxy-combustion reaction to produce CO₂ for a catalytic hydrogenationprocess. The catalytic hydrogenation process may produce either CH₄ orCH₃OH by reacting the CO₂ with H₂. The CH₄ or CH₃OH may be fed into anatural gas grid and is in fluid communication with the oxy-combustionprocess, wherein the CH₄ or CH₃OH may react with O₂ to produce the CO₂that combines with the CO₂ captured from an industrial process. Thecycle comprising the CO₂ streams (both captured CO₂ and CO₂ produced bythe oxy-combustion process), the catalytic hydrogenation, the naturalgas grid, and the oxy-combustion process is exemplary of a carbonneutral natural gas cycle according to embodiments of the currentdisclosure.

According to embodiments of the current disclosure, the driving energyfor the CO₂ utilization and value creation process may be energyproduced by a MSR. The energy produced by a MSR may be used in adesalination process to produce H₂O. The H₂O produced in thedesalination process may produce H₂ and O₂ through electrolysis of theH₂O. The O₂ from the electrolysis process may be used in theoxy-combustion process of the carbon neutral natural gas cycle. The H₂from the electrolysis may be used in the catalytic hydrogenation of thecarbon neutral natural gas cycle, as well as other industrialapplications. Embodiments of the present disclosure may provide anoption of using clean electrical energy produced, for example, by amolten salt reactor (nuclear) with zero CO₂ emission, to convert CO₂into commercial products for a carbon neutral life cycle use of naturalgas.

Green (clean) electricity/energy, as defined herein, means energyproduced with minimum environmental impact. It is representative ofenergy resources and technologies that provide the highest environmentalbenefit, while minimizing environment harm. The U.S. market definesgreen power/electricity as electricity produced from solar, wind,geothermal, biogas, eligible biomass, and low-impact small hydroelectricsources. It may be synonymous with other terms, such as renewableenergy, clean energy, and green energy.

Embodiments of the present disclosure may decrease the CO₂ emissionsinto the atmosphere by a system and process powered by clean/greenenergy. The driving energy of embodiments of the present disclosure maybe green/clean energy generated by a molten salt reactor. The moltensalt reactor may have negligible to no measurable CO₂ emissions. The O₂in the oxy-combustion process according to embodiments of the presentdisclosure and the hydrocarbon fuel produces CO₂ that may otherwise bereleased into the atmosphere. The CO₂ produced by the oxy-combustionreaction may be combined with CO₂ from natural gas production, whereinit is captured and reacted with H₂ to produce product streams, such asCH₄, CH₃OH, or other chemicals (e.g., ethylene and propylene).

The water produced in the desalination process may be used for a varietyof applications. The desalination process of the present disclosure,powered by the green/clean energy generated by a molten salt reactor,may produce pure H₂O that may be used for human consumption andindustrial applications.

Embodiments of the present disclosure may provide a carbon neutral cyclefor the world's future circular carbon economy. Some embodiments of thepresent disclosure form a carbon neutral gas cycle of natural gasproduction, CO₂ capture, CO₂ utilization, CO₂ value creation, and CO₂transportation, all powered with clean/green energy generated from azero CO₂ emission molten salt reactor. Examples of CO₂ value creation inembodiments of the present disclosure include the production of methane,methanol, methanol, hydrogen, and oxygen. The production of methane andmethanol require extensive amounts of hydrogen. According to embodimentsof the present disclosure, the hydrogen may be produced by electrolysisof water, the electrolysis process powered by the zero CO₂ emission MSR.

Embodiments of the present disclosure decrease CO₂ emissions in theproduction of methane and methanol by producing the hydrogen necessaryto produce methane and methanol using clean resources. These cleanresources may be desalination and electrolysis powered by a source withzero CO₂ emissions, such as a molten salt reactor.

Embodiments of the present disclosure may reduce emission of NOx, byintegrating an oxy-combustion process for natural gas power plants, asdescribed above.

Embodiments of the present disclosure may increase potable waterproduction, improve refinery operations, improve hydrogen economicactivities with the use of green energy, and increase oil recovery bysupporting EOR operations with high-salinity fluids. Excess methane ormethanol produced in the carbon neutral natural gas cycle may beexported or converted into other useful products. Similarly, excesshydrogen and oxygen not used in the carbon neutral natural gas cycle maybe exported for other industrial or commercial uses.

Although only a few example embodiments have been described in detailabove, those skilled in the art will readily appreciate that manymodifications are possible in the example embodiments without materiallydeparting from this invention. Accordingly, all such modifications areintended to be included within the scope of this disclosure as definedin the following claims. In the claims, means-plus-function clauses areintended to cover the structures described herein as performing therecited function and not only structural equivalents, but alsoequivalent structures. Thus, although a nail and a screw may not bestructural equivalents in that a nail employs a cylindrical surface tosecure wooden parts together, whereas a screw employs a helical surface,in the environment of fastening wooden parts, a nail and a screw may beequivalent structures. It is the express intention of the applicant notto invoke 35 U.S.C. § 112, paragraph 6 for any limitations of any of theclaims herein, except for those in which the claim expressly uses thewords ‘means for’ together with an associated function.

What is claimed:
 1. A system for a carbon neutral cycle of natural gasproduction, the system comprising: a molten salt reactor configured togenerate zero carbon dioxide (CO₂) emissions electricity; a desalinationunit configured to (i) receive the zero-CO₂ emissions electricity fromthe molten salt reactor and (ii) produce a desalinated water; anelectrolysis unit configured to (i) be powered by the zero-CO₂ emissionselectricity generated by the molten salt reactor and (ii) generatehydrogen (H₂) and oxygen (O₂) from the desalinated water; anoxy-combustion unit configured to receive and combust a hydrocarbon fuelwith the O₂ from the electrolysis unit to produce electricity and carbondioxide (CO₂); a CO₂ capture system adapted to capture the CO₂ producedby the oxy-combustion unit; and a catalytic hydrogenation unitconfigured to receive and convert H₂ from the electrolysis unit and CO₂from the CO₂ capture system to produce the hydrocarbon fuel.
 2. Thesystem of claim 1, wherein the hydrocarbon fuel comprises methane. 3.The system of claim 1, wherein the hydrocarbon fuel comprises methanol.4. The system of claim 1, wherein the CO₂ capture system is configuredto receive CO₂ sequestered from a natural gas production unit and/orwherein the CO₂ capture system is configured to capture CO₂ from a rawor partially processed natural gas stream.
 5. The system of claim 1,further comprising a flow line for recovering or outputting at least aportion of the hydrocarbon fuel produced by the catalytic hydrogenationunit as a product.
 6. The system of claim 1, further comprising a flowline for feeding at least a portion of the hydrocarbon fuel produced bythe catalytic hydrogenation unit to the oxy-combustion unit.
 7. Thesystem of claim 1, further comprising a flow line for feeding at least aportion of the hydrogen produced by the electrolysis unit to a refineryand/or a hydrogen capture system for recovering the hydrogen produced bythe electrolysis unit as a product.
 8. The system of claim 1, furthercomprising a downstream conversion process configured to receive aportion of the hydrocarbon fuel.
 9. A method for a carbon neutral cycleof a natural gas production, the method comprising: generatingelectricity with a molten salt reactor configured to generate zerocarbon dioxide (CO₂) emissions; powering a desalination unit with theelectricity from the molten salt reactor, producing desalinated water(H₂O) with the desalination unit; producing hydrogen (H₂) and oxygen(O₂) from the desalinated water (H₂O) with an electrolysis unit;introducing the hydrogen produced by the electrolysis unit to acatalytic hydrogenation unit; reacting captured CO₂ and the hydrogengenerated from the desalination unit by catalytic hydrogenation in acatalytic hydrogenation unit, wherein the reaction produces ahydrocarbon fuel; introducing the hydrocarbon fuel into anoxy-combustion unit; producing CO₂ in the oxy-combustion unit byreacting the hydrocarbon fuel with the oxygen from the electrolysisunit; capturing CO₂ from the oxy-combustion unit; and introducing thecaptured CO₂ to the catalytic hydrogenation unit.
 10. The method ofclaim 9, wherein the hydrocarbon fuel comprises methane.
 11. The methodof claim 9, wherein the hydrocarbon fuel comprises methanol.
 12. Themethod of claim 9, wherein the desalination unit produces a highsalinity product, the method further comprising using the high salinityproduct in an enhanced oil recovery process.
 13. The method of claim 9,further comprising capturing CO₂ sequestered from a natural gasproduction unit and/or capturing CO₂ from a raw or partially processednatural gas stream and combining it with the captured CO₂.
 14. Themethod of claim 9, further comprising outputting at least a portion ofthe hydrogen produced by the electrolysis unit to a refinery and/or ahydrogen capture system for recovering the hydrogen as a product. 15.The method of claim 9, further comprising outputting at least a portionof the hydrocarbon fuel produced by the catalytic hydrogenation unit asa product.
 16. The method of claim 9, further comprising feeding aportion of the hydrocarbon fuel to a downstream conversion process.